Dynamic mechanical behavior and cracking mechanism of cross-jointed granite containing a hole

Abstract

The cavity disasters induced by dynamic disturbances are hazards to the cavity safety and may cause substantial damage to the entire subsurface project. The dynamic mechanical responses of the cavern are crucially important in rock engineering design and stability analysis. In this article, the dynamic mechanical and cracking behaviors of the jointed surrounding rock of the cavern were investigated experimentally by testing cross-jointed granite containing a hole using a split Hopkinson pressure bar. The results indicate that the dynamic peak strength and elastic modulus decrease as β increases from 15° to 45° and increase gradually as β varies from 45° to 75°, and those two parameters show an overall increasing trend with increasing impact pressure. The reflected and absorbed energy ratios first increase and then decrease with increasing β, while the transmitted energy ratio first decreases and then increases. Under the same impact pressure, the absorbed energy ratio is far higher than the reflected and transmitted energy ratios. With increasing impact pressure, the transmitted and absorbed energy ratios increase overall, while the reflected energy ratio generally decreases. Additionally, the cracking process and final failure modes of the samples show a significant joint structure effect and strain rate effect. Nevertheless, the tensile cracks along the impact direction play a dominant role in the dynamic fracture, and tensile failure is the main failure type, with shear failure occurring locally. These findings provide the theoretical basis for preventing dynamic disasters in the cavity and are of great significance to rock engineering safety.

Keywords

• Cross-jointed granite
• Mechanical behavior
• Energy ratio
• Cracking mechanism
• Split Hopkinson pressure bar test